Research area: „Advanced MRI contrasts in chemical engineering“

Dr. Stefan Benders

Magnetic Resonance Imaging (MRI) is a powerful technique able to leverage several contrasts to gain non-intrusive, tomographic information. While the technique has seen wide application and development in the medical field, the usage in the engineering field has been limited. While there are notable contributions in the field, many of the capabilities possible in clinical MRI have not been applied to chemical engineering yet. The application within this field benefits from a certain scale, limited in the past by vertical micro-imaging systems. The introduction of the TUHH process imaging MRI enables the measurements of such systems and opens many possibilities. Many applications already benefit from basic MRI contrasts such as spin density, relaxation or velocity, yielding valuable information.

NMR or MRI offers many more contrasts, though. Therefore, my research focuses on making these contrasts available to MRI in chemical engineering and analyze complex samples. One of the main goals is to visualize chemical reactions in relevant reactor geometries in good temporal resolutions.

Contrasts available with MRI:

Classical contrasts:

  • Spin density : spin density is the most common contrast. It denotes the amount of nuclear spins (commonly 1H) in a pixel/voxel.
    • Application examples: Visualization of liquid holdup in trickle beds, gas content in bubble columns, visualization of fluidized beds
  • Relaxation: Relaxation can make different sites in a reactor, as well as porous materials, distinguishable.
    •  Application examples: Porous carriers, gel
  • Velocity: MR is able to measure velocity without tracer molecules.
    • Application examples:
      • Liquid flow in pipe-like reactors, flow though structures
      • Investigation of stirred tank reactors
      • Measurements of shear rates
      • Flow in fluidized beds
      • Flow in microfluidic reactors

Advanced contrasts

  • Diffusion: MR is able to spatially resolve the self-diffusion coefficient in multiple directions. More complex diffusion measurements can also be performed.
    • Applications: measurements of diffusion in porous materials such as catalyst pellets
  • Temperature: There are several ways to measure temperature with MR (Relaxation, Proton Resonance shift, Conductivity, Chemical shift imaging).
    • Applications: Temperature distributions in reactors, analysis of complex materials
  • Conductivity: MR is able to measure conductivity with reduced spatial resolution.
    • Applications: Electrochemical materials, …
  • Statistical NMR: Bayesian analysis has been shown to be a powerful tool to analyze bubble size and pore size distributions.
    • Applications: Bubble column reactors, porous media
  • Chemical shift/information: Chemical information is a unique feature of MR based methods. Spatially resolving this in good spatiotemporal resolution poses a major challenge. Our goal is to accelerate the procedures to enable reaction monitoring in relevant temporal resolution. This will be a big step towards monitoring of chemical reactions in real reactor geometries.

I am also interested in various other systems and methodologies, such as

  • Fast relaxometry techniques in Low-Field NMR
  • Visualization of the magnetohydrodynamic effect
  • Visualization of mechanical stress within samples
  • Novel coil designs to measure inside metals
  • FRANK excitation NMR
  • Simulation of MR sequences and reconstruction

Associated students:

Bachelor, Master and research students:

Former students:

  • Tarik Kaya